Q = CV
Q: amount of charge in Couloumbs
C: capacitance in Farads
V: voltage in Volts
Separation between plates: The attraction between positive charge on one plate and negative charge on
the other plate causes the capacitor to hold charge. Increasing the plate separation reduces the
attraction of opposite charges thereby reducing the capacitance, so:
C is proportional to 1/d where d is the separation distance between the plates.
Area of the plates: The repulsion of like charges on a single plate limits the amount of charge that can be
stored. Increasing the area of a plate increases the amount of charge that can be stored before
equilibrium is reached, thus increasing the capacitance, so:
C is proportional to A where A is the area of the plates.
Dielectric constant: A third physical property can also influence the capacitance of a parallel plate
capacitor. The material used as the insulator between the plates can increase the capacitance if the
molecules in the material possess an electric dipole moment. Such polar molecules have one side slightly
more positive as compared to the other side of the molecule. A good example is liquid water (H2O).
When dielectric materials are placed between capacitor plates, the dipoles align in a manner that
enhances the attraction of positive charges on one plate and negative charges on the other plate, so
C is proportional to K where K is the dielectric constant
The dielectric constant, K>=1. In the case of air (which does not have an electric dipole moment), K = 1.Κ ≥1
In other materials with electric dipole moments, K > 1.
𝐶 = ε0𝐾 (𝐴/D) where ε0=8.85*10^-12
Supplied Coil Turn Amount / Measured Coil turn
amount is approximately equal to the gain.
Voltage Gain = Output Voltage / Input Voltage
One can conclude that as the impedance of an inductor increases with increasing frequency, it will eventually equal the impedance of
the resistor. When 𝑅 = ω𝐿, the phase goes to 45𝆩 and the point at which this occurs is called the
cut-off frequency. This occurs when ω = R/L = ωc
ω: Angular frequency which is equal to 2𝝅f where f us frequency in hertz.
Voltage across the capacitor as a function of time V(t) = V0e–(t/RC)
RC is the time constant and is in units of seconds.
(resonance frequency) FR=
1
2π 𝐿𝐶
Ohm’s law V=IR
V: voltage difference
I: Current in amps A
R: resistance in ohms Ω
Voltage in series R1+R2=R
1
1
1
Parallel circuit 𝑅 = 𝑅1 + 𝑅2
Junction Rule: the total current flowing into any point is zero at all times where we use
the convention that current into a point is positive and current out of the point is
negative. Σ 𝐼(𝑐𝑢𝑟𝑟𝑒𝑛𝑡) = 0
Loop Rule: the sum of the voltage drops around any closed loop must equal zero where
the drop is negative if the voltage decreases and positive if the voltage increases in the
direction that one goes around the loop. Σ 𝑉 = 0
Sum of currents (i1 - iA - iB)
Qfinal = Qred+QBlue
Qinitial = Qred +QBlue
A charge added to a conductor then grounded should sum to zero. Therefore if a n charge is added, grounded and removed then the
charge on the conductor is -n.